Structure of Flowering Plants

TYPICAL STRUCTURE OF THE FLOWERING PLANT

Part	Function
Root	Absorbs water and minerals from soil Anchors the plant in the soil Some modified to store food. E.g., carrots. Vegetative propagation occurring in some e.g. Dahlia
Stem	Support aerial plant parts Transport food e.g. glucose from leaves in phloem Transport water and minerals from roots to leaves in xylem vessels. Some are modified to store food, e.g. (potato tubers) Exchange of gases occur through lenticels (tiny openings in stems of shrubs and trees) Vegetative propagation occurring in some e.g. (potato tubers, strawberry runner)
Leaves	Site of Photosynthesis Exchange of gases through stomata Transpiration Vegetative Propagation in some (Bryophyllum-produces plantlets on leaves) Some can be modified to store food e.g. Rhubarb, Celery, Cabbage.
Flower	Function in sexual reproduction Anther of stamen produces male gametes in pollen grains Ovule of carpel produces female gamete=egg Fertilisation = fusion of male and female gametes occurs in the ovule. The fertilized ovule becomes a seed.
Buds	Apical buds provide for growth in length Auxiliary (lateral) buds produce side branches and flowers. Some buds involved in vegetative propagation. E.g. onion
Node	Point of attachment of leaf to stem
Internode	The region of the stem between two nodes.

Differences between a dicot stem and a monocot stem

DICOT:	MONOCOT:
Vascular Bundles arranged orderly in a ring	Vascular bundles are scattered
Has cambium between xylem and phloem in the vascular bundles	No cambium present.

Structure of a leaf

Note:

Leaves are thin and flat
Stomata are present for exchange of gases
Air spaces in the ground tissue for rapid diffusion of gases
Some leaves have a waxy layer called a cuticle to reduce water loss. (non-cellular layer)

A Meristem

A meristem is a group of cells that continuously divide by mitosis for growth.

Apical meristems are found near root and shoot tips and they allow for growth in length.
Lateral meristems e.g. cambium allow for growth in width.

Meristimatic tissue divides to produce new cells. When these cells differentiate they give rise to :

DERMAL TISSUE:
forms the protective covering of plants

GROUND TISSUE:
Fills the interior of the plant
Involved in photosynthesis or food storage. Also gives strength and support to the plant

VASCULAR TISSUE:
Xylem transports water and minerals
Phloem transports food e.g glucose, amino acids.

Roots

Structure of a T.S of a root:

Recognised by: star shaped xylem

the presence of root hairs

Strucure of L.S of a root:

Root Cap	Protects Roots growing down through soil.
Meristimatic Zone	Cells divide by mitosis for growth
Zone of Elongation	Plant growth regulators stimulate these cells to get longer.
Zone of Differentiation	Cells in this region develop into different tissue tyoes. E.g. ground, vascular and dermal.

Phloem and Xylem

PHLOEM:

Phloem is considered to be a living tissue as companion cells have a nucleus.

Function of phloem:

Transport of food e.g glucose amino acids and growth regulators. This movement of food through phloem is also called translocation.

Phloem Sieve Tubes:

Long tubular structures
Formed when individual cells called sieve elements join end to end
End walls develop pores called sieve plates allowing passage of materials from one element to another
Cytoplasm of each element remains but the nucleus degenerates
No lignin present

Companion Cells:

Accompany sieve tubes
Have a nucleus and cytoplasm
Control the activities of sieve tube elements

XYLEM:

There are two types of xylem- xylem vessels and xylem tracheids.
Both types of xylem are dead and hollow at maturity-(nucleus and cytoplasm are dead)

Functions of Xylem:

Transport of water and minerals from roots
Old xylem forms the wood in trees and gives mechanical support.

Xylem Vessels:	Xyelm Tracheid Cells:
Tubular structures formed when cells join end to end and the end walls dissolve away forming a continuous tube.	Long tapering cells
Have pits on their side walls to allow water to pass from one vessel to another	Hollow inside when mature
Wider than tracheids	Tracheids overlap
More efficient at transporting water	Water passes from tracheid to tracheid through pits
Very common in flowering plants	More primitive than vessels. Also only type of xylem found in Confiers e.g. pine trees
Walls strengthened with lignin	Walls strengthened with lignin

DIFFERENCES BETWEEN DICOTS AND MONOCOTS:

DICOTS	MONOCOTS
May be woody or herbaceous	Almost always herbaceous
Flower part in units of 4 or 5	Flower parts in units of 3
Have net leaf veination	Have parallel leaf veniation
Vasucular bundles in an orderly array in a stem, may be circular or opposite	Scattered vascular bundles in stem
Have two cotyledons or seed leaves	Have one cotyledon or seed leaf.
Examples include: beans, peas, peanuts	Examples include: daffodils, tulips, grasses.

Structure of Flowering Plants

TYPICAL STRUCTURE OF THE FLOWERING PLANT

Part

Function

Differences between a dicot stem and a monocot stem

DICOT:

MONOCOT:

Structure of a leaf

A Meristem

Roots

Phloem and Xylem

PHLOEM:

XYLEM:

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